The present invention relates to a semiconductor device having a switching element and, more particularly, to a semiconductor device having an improved mounting structure for thyristors, power transistors, and the like used in the field of power electronics.
Recently, in the field of power electronics control for industrial pumps, fans, and the like, efforts have been made to effectively use energy by using inverter devices. The major portion of such an inverter device is made of a semiconductor switching element for switching currents.
As semiconductor switching elements, thyristors, power transistors, and the like have been often used. Recently, a GTO (Gate Turn-off Thyristor), an IGBT (Insulated Gate Bipolar Transistor), an IEGT (Injection Enhanced Gate Transistor), and the like have been widely used.
Each of these semiconductor switching elements includes three electrodes, namely a positive (emitter) electrode, a negative (collector) electrode, and a control (gate) electrode, which are named differently depending on the types, and performs switching operation by controlling currents and voltages through the control electrode.
When these elements are mounted in a package, the positive and negative electrodes generate a considerable amount of heat because of the flow of large currents therein and switching operation. Careful consideration must therefore be given to current capacity and a heat dissipation structure. Since no large current flows in the control gate, no special heat dissipation measures are required for it.
In many cases, a plurality of semiconductor switching elements are simultaneously used depending on control targets.
FIG. 1 is a sectional side view of a conventional semiconductor device having a plurality (one pair in FIG. 1) of IGBTs (or IEGTs) as semiconductor switching elements mounted side by side on a board.
Two IGBTs 1a and 1b respectively have emitter electrodes 2a and 2b formed on their surfaces. The emitter electrodes 2a and 2b are respectively connected to wirings 10a and 10b by soldering.
Gate electrodes 6a and 6b are formed on the end faces of the upper surfaces of the IGBTs 1a and 1b. The gate electrodes 6a and 6b are respectively connected to wirings 10c and 10d by soldering.
Collector electrodes 9a and 9b are formed on the lower surfaces of the IGBTs 1a and 1b. The collector electrodes 9a and 9b are respectively connected to surface copper patterns 14a and 14b on a DBC (copper-clad ceramic) board 3 by soldering.
The electrodes 2a, 2b, 6a, and 6b on the upper surfaces of the IGBTs 1a and 1b and the electrodes 9a and 9b on the lower surfaces are metallized to allow soldering.
Note that a metallization method is not limited to a specific one, and a method of forming a metal layer on the surface of an aluminum electrode using titanium, platinum, gold, or palladium, a method of coating an aluminum electrode with nickel or the like, is properly used. A heat sink 12 is soldered to the lower surface of the board.
In this structure, the emitter electrode 2a on the IGBT 1a is electrically connected to the collector electrode 9b on the IGBT 1b through the wiring 10a and the surface copper pattern 14b.
FIG. 2 is a sectional side view of another conventional semiconductor device having a plurality (one pair in FIG. 2) of IGBTs mounted on a board.
Two IGBTs 1a and 1b respectively have emitter electrodes 2a and 2b formed on their lower surfaces. The emitter electrodes 2a and 2b are respectively connected to surface copper patterns 14a and 14b on a DBC (copper-clad ceramic) board 3 by soldering.
Gate electrodes 6a and 6b are formed on the end faces of the upper surfaces of the IGBT31a and 1b. The gate electrodes 6a and 6b are respectively connected to surface copper patterns 7a and 7b on the DBC board 3 by soldering.
Collector electrodes 9a and 9b are also formed on the lower surfaces of the IGBTs 1a and 1b. The collector electrodes 9a and 9b are respectively connected to wirings 10d and 10c by soldering.
The electrodes 2a, 2b, 6a, 6b, 9a, and 9b on the upper and lower surfaces of the IGBTs 1a and 1b are metallized to allow soldering as in the case shown in FIG. 1. Similarly, a heat sink 12 is also soldered to the lower surface of the board 3.
In this structure, the emitter electrode 2b on the IGBT 1b is electrically connected to the collector electrode 9a on the IGBT 1a through the wiring 10d and the surface copper pattern 14b.
In each of the conventional mounting structures shown in FIGS. 1 and 2, each connection member has a connect portion perpendicular to the board 3. Therefore, a large inductance component is produced by each connect portion that is perpendicular to the board 3.
In addition, since connection members such as the wirings 10a and 10d must be arranged between two chips, the size of the package becomes large.
If wirings are routed in a complicated manner to reduce a size of the package, connection members need not necessarily be arranged between two chips. In consideration of wiring resistances and inductances as electric circuit characteristics, however, it is inadvisable to route the interconnections in a complicated manner.